Composite Decking Estimator
Calculate boards, fasteners, and estimated costs for your project.
Project Estimate
*Includes a 10% waste factor for cuts and errors.
How to Estimate Your Composite Decking Project
Planning a composite deck requires more precision than traditional wood. Composite boards expand and contract with temperature changes, meaning specific gapping and joist spacing are critical for a long-lasting finish.
Understanding the Calculation
To determine the number of boards, we first calculate the total square footage of the deck area. We then divide that by the square footage of a single board (including the gap between boards). For example, a standard 5.5-inch board with a 1/4-inch gap actually covers 5.75 inches of width.
- Board Area: (Board Width + Gap) × Board Length.
- Waste Factor: We always add 10% to the total board count to account for end-cuts, staggered patterns, and potential mistakes.
- Fasteners: Most composite systems require hidden fasteners. Generally, you will need about 2.5 to 3 fasteners per square foot of decking, depending on joist spacing.
Key Considerations for Composite
Unlike pressure-treated lumber, composite decking is not structural. It requires a solid sub-frame. Most manufacturers recommend a maximum joist spacing of 16 inches on center for residential decks, or 12 inches on center if you are laying the boards diagonally.
Example Estimate
If you have a 12′ x 16′ deck (192 sq. ft.) and you use 16-foot long boards that are 5.5″ wide:
- One board covers approximately 7.66 sq. ft. (including gap).
- 192 / 7.66 = ~25 boards.
- Adding 10% waste = 28 boards total.
- If boards cost $45 each, your estimated material cost for decking is $1,260.